Abstract: The Foucault pendulum is well kmown as one of the most beautiful physics experiments, but the explanation of the Foucault pendulum is always difficult in the college physics course. Unlike the method of Newtonian mechanics, which introduces the Coriolis force to explain the rotation of the Foucault pendulum, this paper uses a geometric method to analyze the Foucault pendulum, and it is shown that the rotation of the Foucault pendulum is the result of translating the velocity vector of the pendulum on the sphere. Finally, the equivalence of the geometric method and the Newtonian mechanics method is proven.